Duty cycle regulated power supply



1967 L. E. YEARLEY DUTY CYCLE REGULATED POWER SUPPLY Nov.

Filed Feb. 15, 1965 Power Stage 7n- Amplifier I F IG. 2.

524 I Ju U11 um mm INVENTOR A 7' TOR/YE)" United States Patent 3,351,840DUTY CYCLE REGULATED POWER SUPPLY Lawrence E. Yearley, Vista, Califl,assignor to General Precision, Inc., a corporation of Delaware FiledFeb. 15, 1965, Ser. No. 432,564 1 Claim. (Cl. 321-45) ABSTRACT OF THEDISCLOSURE A regulated power supply responsive to interlaced pulses ofpredetermined polarity applied to a pair of inputs is provided whereinthe short input pulses initiate conduction in both a transistor in theprimary winding circuit of a transformer and in a silicon controlledrectifier in the circuit of a feedback winding inductively coupled tothe transformer primary winding. Conduction in the transistor andsilicon controlled rectifier increases until saturation in thetransformer is reached and then diminishes until bias cannot sustainconduction. An elongated pulse is produced in the transformer secondary,is amplified, rectified and filtered to produce a constant,unidirectional potential.

Noise is minimized by blocking diodes in respective inputs and potentialapplied to transistors is limited by diodes connected between collectorsand one electrode of a zener diode the other electrode of which isgrounded.

This invention relates to an electrical power supply and moreparticularly to a novel and improved regulated electrical power supplyconsisting of a push-pull, pulse amplifier which transforms interlacedpulses into constant amplitude drive pulses used by subsequent powerstages or the like.

Briefly described, this invention provides a means of deriving aconstant regulated direct voltage supply with a unique push-pullamplifier. Interlaced electrical pulses are alternately applied totrigger electrodes of silicon controlled rectifiers which providecurrent flow to a saturable core transformer which has a feedbackwinding coupled back into the anode of the silicon controlled rectifier.This regenerates the silicon controlled rectifier, keeping it conductingafter the initial pulse has diminished, and it will continue conductingduring the saturation time of the core of the transformer. The outputsof the transformer feed a power stage transformer and the outputtherefrom is rectified and all the subsequent noise is filtered outwhich provides the constant voltage regulated power supply.

The principal object of this invention is to provide a novel andimproved amplifier for developing a quasisquare wave with a variabletime interval between alternate half cycles of drive power.

In the drawings:

FIGURE 1 is a schematic drawing illustrating one embodiment of thisinvention;

FIGURE 2 is a graphic diagram illustrating representations of thevarious pulses throughout the schematic drawing of FIGURE 1.

Referring now to the accompanying drawings, wherein like referencenumerals indicate like or corresponding parts throughout the severalviews, there is shown in FIGURE 1 a pair of input terminals and 12 whichreceive a pair of interlaced electrical signals in the form of spikes asshown in FIGURE 2 and numbered 10A and 12A to correspond to theirterminal numbers. Signals of this type originate in an oscillator whichproduces alternate interlaced pulses and are well known in the art.

A pair of blocking diodes 14 and 16 may next be employed to limit thedirection of current flow wherein diode 14 is coupled to the triggerelectrode of a silicon controlled rectifier 18; therefore, signals onthe input terminal 10 are used to trigger the silicon controlledrectifier conducting. This signal is also simultaneously applied to thebase of transistor 20 rendering it conductive and causing current toflow from a +28 voltage supply designated by the numeral 22 through theprimary winding 24 of a saturable core transformer 26. A saturable coretransformer 26 will begin saturating causing an induced current flowinto the feedback winding 28, causing current to flow into the anode ofthe silicon controlled rectifier 18 and subsequently keeping the siliconcontrolled rectifier 18 conducting even though the oscillator signal onterminal 10 has diminished. Capacitor 29 suppresses voltage transientswhich would cause triggering of the silicon controlled rectifier 18.Current will continue flowing in the feedback winding 28 due totransistor 20 conducting and cause the silicon controlled rectifier tolock on. When the core of transformer 26 is completely saturated, thevoltage induced by transformer 26 diminishes, reducing the drive signalto transistor 20. The reduced drive signal allows transistor 20 to ceaseconducting. Diminishing current in winding 24 induces voltage of theopposite polarity which appears on the anode of the silicon controlledrectifier 18, turning it ofi, and, as is inherent with this type ofcomponent, it will not conduct again until a signal is received on itstrigger electrode. At this time the silicon controlled rectifier 18 willoperate as a blocking diode and prevent current from flowing into thebase of transistor 20.

An alternate pulse is now applied to the terminal 12 and to the triggerelectrode of the silicon controlled rectifier 30 rendering itconductive. The alternate pulse is interlaced as previously mentionedwith the signal on terminal 10 and is illustrated by the graph 12A ofFIG- URE 2. This pulse is also applied to the base of transistor 32,rendering this component conductive. Current will now flow from theterminal 22 through the primary winding 34 of the transformer 26. Avoltage is induced into the feedback winding 36 and likewise againlocking on the silicon controlled rectifier 30.

A means of limiting the voltage applied to the transistors 20 and 32 isprovided by the diodes 40, 42 and 44. The diode 42 has a specificbackbiased zener voltage which provides that any voltage over thespecific zener voltage will be conducted to ground. Other means could beemployed or a lower voltage on terminal 22 may be used, thereby allowingthe diodes 40, 42 and 44 to be eliminated.

Outputs from the transformer 26 are taken from a pair of secondarywindings and signals produced therefrom are in the form of three-stagequasi-square wave forms of opposite polarities with a pulse durationtime equal to the saturation time of the saturable core of transformer26. These signals are illustrated by the graphs 50A and 52A in FIGURE 2.

Transformer output Winding 50 has one end thereof coupled to the base ofa transistor 56 through a current limiting resistor 54. The other end ofthe secondary winding 52 is coupled through the limiting resistor 55 tothe base of transistor 58. A center tap between the secondary windings50 and 52 is coupled to the emitters of both transistors 56 and 58. Thecollectors of transistors 56 and 58 are coupled to the primary windingsof a power stage transformer 60, which has a center tap on the primarywindings coupled directly to the terminal 22 and the 28 volt powersupply. Diodes 62, 64 and 66 are again provided to limit the voltageapplied to the collectors of transistors 56, 58 by coupling the anodesof diode 62 to the collector of transistor 56, and the anode of diode 64to the collector of transistor 58, and coupled in the anodes from diodes62 and 64 directly into the cathode of diode 66 which has a specificzener voltage and the anode of diode 66 coupled to ground.

The secondary winding of the transformer 60 is coupled to a pair ofrectifier diodes 68 and 70, and the outputs therefrom are coupledtogether into a filter formed of the inductor 72 and the capacitor 74.The output of the rectifier before it is presented to the filter atpoint on the lead numeral 80 is illustrated in the graph 80A of FIGURE2. The filter 71 removes all of the returnto-zero spikes presenting theconstant current output.

The power stage 59, the rectifier 69, and the filter 71 are illustrativeof one particular power stage that can be used with this invention.Obviously, other modifications such as different types of power stages,etc., can be added to this invention without departing from the spiritand scope as set forth in the appended claim.

What is claimed is:

A regulated electrical power supply including a pushpull amplifiercomprising a first input path and a second input path each havingunidirectionally conducting means interposed therein and adapted toreceive and pass alternately interlaced electrical signals of apredetermined polarity, first and second silicon controlled rectifierseach having an anode, a cathode, and a control element connected to saidunidirectional devices and alternately enabled by said interlacedpulses, first and second transistors each having an emitter, a collectorand a base, a saturable core transformer having a center tapped primarywinding and respective ends of said primary winding connected tocollector electrodes of said transistors, the emitter electrodes of saidtransistors being connected to ground and the bases of said transistorsbeing connected to respective cathodes of said silicon controlledrectifiers, said transformer having a pair of feedback windings eachhaving one end grounded and the other ends of said feedback windingsbeing connected to respective anodes of said silicon controlledrectifiers, a further pair of unidirectional devices having anodesconnected to respective collectors of said transistors and cathodesconnected together, a zener type diode having a cathode connected to thecathodes of said further pair of unidirectional devices and an anodeconnected to ground, said transformer having a secondary winding coupledto push-pull power amplifier means, rectifier and filter means coupledto said power amplifier means.

References Cited UNITED STATES PATENTS 3,030,589 4/1962 Kadri 331113.13,219,906 11/1965 Keller et al 321 3,222,618 12/1965 Ressler 32l-2 XR3,267,349 8/1966 Krause 3212 XR 3,305,760 2/1967 Davis et a1. 32l45 JOHNF. COUCH, Primary Examiner.

WM. SHOOP, Assistant Examiner.

